Pedigree analysis worksheet - Free Printable

It looks like you've uploaded a pedigree analysis worksheet, but the actual questions that go with the pedigree chart are not visible in your image. However, I can help you analyze the pedigree chart and explain how to interpret it so you can answer typical questions about inheritance patterns.

Let’s break down what we see and then provide a full explanation of the likely pattern and how to solve common pedigree problems.

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🔍 Understanding the Pedigree Chart

#### Symbols:
- Circle = Female
- Square = Male
- Solid (filled) shape = Person has the trait
- Half-shaded shape = Carrier (heterozygous, but does not show the trait)
- Unshaded shape = Does not have the trait and is not a carrier

> In this chart:
> - Blue = Completely shaded → has the trait
> - Orange = Unshaded → no trait, not a carrier
> - There are no half-shaded symbols, so carriers are not indicated here.

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🧬 Step-by-Step Analysis

We are analyzing the inheritance pattern of a trait across three generations:

#### Generation I:
- Ann (female): Unshaded → No trait
- John (male): Shaded → Has trait

#### Generation II (Children of Ann & John):
- Bert: Shaded → Has trait
- Norris: Shaded → Has trait
- Joan: Unshaded → No trait
- Sue: Unshaded → No trait
- Fred: Shaded → Has trait
- David: Shaded → Has trait
- Alice: Unshaded → No trait

#### Generation III (Grandchildren):
- Jenine, Jill, Louise, Janice, Marie: All unshaded → No trait
- Frank, George, Tom: All shaded → Have trait

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✔ Key Observations

1. John (Generation I) has the trait.
2. Ann (Generation I) does not have the trait.
3. Their children: Bert, Norris, Fred, David have the trait; Joan, Sue, Alice do not.
4. The trait appears in both males and females.
5. Some individuals who do not have the trait (like Ann, Joan, Sue, Alice) have children who do have the trait — meaning they must be carriers.
6. But since there are no half-shaded symbols, we assume this is a dominant or recessive trait.

Let’s test possible inheritance patterns.

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🧠 Determining the Pattern

#### Is it Dominant?
- If the trait were dominant, then every person with the trait must have at least one parent with the trait.
- This is true: all affected individuals (blue) have John as a parent → he has the trait.
- But also, Ann does not have the trait, yet her children (Bert, Norris, etc.) do → So Ann must be a carrier.
- But if it's dominant, then unaffected individuals cannot pass on the trait unless they have it.

Wait — this is a problem.

In dominant traits, if someone doesn’t have the trait, they cannot pass it on.

But here:
- Ann does not have the trait.
- Yet she has children who do (e.g., Bert, Norris).
- That means Ann must carry the allele → which only happens in recessive traits.

So this suggests the trait is recessive.

But wait — John has the trait, and Ann does not. They have children who do have the trait.

If the trait is recessive, then both parents must be carriers for a child to express it.

But John has the trait → if it’s recessive, then he is homozygous recessive (aa).

Ann does not have the trait → could be AA or Aa.

For their children to have the trait (aa), they must get a from both parents.

So:
- John = aa
- Ann = Aa → carrier (but not showing trait)

Then their children:
- 50% chance of being aa (have trait)
- 50% chance of being Aa (carrier, no trait)

This matches:
- 4 out of 7 children have the trait → roughly 50% → consistent with recessive inheritance.

Also:
- Children of Joan (who is unaffected) and Norris (affected) → Frank has the trait.
- Norris = aa
- Joan = ? → must be Aa (carrier) to have an affected child
- Then Frank = aa → possible

Similarly:
- Sue (unaffected) and Fred (affected) → George and Tom are affected → both must be aa
- Fred = aa
- Sue = Aa → carrier
- Then 50% chance → George and Tom both affected → possible

And:
- David (affected) and Alice (unaffected) → all three children (Louise, Janice, Marie) are unaffected → no trait
- David = aa
- Alice = AA or Aa
- If Alice were Aa → 50% chance of affected kids
- But none are affected → so Alice is likely AA → not a carrier

That fits.

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✔ Conclusion: The trait is Autosomal Recessive

Because:
- Affected individuals have two copies of the recessive allele.
- Unaffected individuals can still be carriers.
- Trait skips generations (e.g., Ann and John → some kids affected, others not).
- Both sexes are affected equally.

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📌 Typical Questions You Might Be Asked

Since the actual questions aren't visible, here are common ones and their answers based on this chart:

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#### ❓1. What type of inheritance pattern is shown?
Answer: Autosomal recessive.

> Reason: Affected individuals have unaffected parents (Ann and John), and the trait appears in both sexes without bias.

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#### ❓2. What is the genotype of Ann?
Answer: Heterozygous (Aa) – carrier.

> She does not have the trait, but she passed the recessive allele to her children who do.

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#### ❓3. What is the genotype of John?
Answer: Homozygous recessive (aa).

> He shows the trait → must be aa.

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#### ❓4. What is the probability that Joan and Norris have another child with the trait?
Answer: 50%

> Norris = aa
> Joan = Aa (since she is unaffected but has an affected child, Frank)
> Cross: Aa × aa → 50% aa (affected)

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#### ❓5. Can Louise have children with the trait?
Answer: Only if her partner is a carrier or affected.

> Louise is unaffected → genotype is either AA or Aa.
> Since her father (David) is aa, and mother (Alice) is likely AA → Louise is Aa (carrier).
> So yes, she can pass the allele to offspring if her partner is also a carrier or affected.

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#### ❓6. Is the trait sex-linked?
Answer: No, it is autosomal.

> Males and females are affected equally. Also, affected males pass the trait to daughters (e.g., John → Bert, Norris, Fred, David), which would not happen in X-linked recessive (since males pass Y to sons, X to daughters).

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✔ Summary

| Feature | Observation |
|--------|-------------|
| Affected individuals | Blue squares/circles |
| Unaffected | Orange |
| Pattern | Autosomal recessive |
| Carrier status | Not shown directly, but inferred from family history |
| Key evidence | Affected individuals have unaffected parents → recessive |

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If you can share the actual questions from the worksheet, I can give specific answers tailored to them.

But based on the chart, the trait is autosomal recessive, and most questions will revolve around identifying genotypes, probabilities, and inheritance patterns.

Let me know if you'd like a genotype chart or a Punnett square for any specific cross!